During the isovolumetric contraction phase of the cardiac cycle, which of the following is TRUE?

• A Aortic valve is open; mitral valve is closed; ventricular volume is constant
• B Both mitral and aortic valves are closed; LV pressure rises rapidly; ventricular volume is constant ✓
• C Mitral valve closes; aortic valve opens simultaneously; ventricular pressure peaks
• D Both valves are open allowing rapid LV filling at near-constant pressure

Explanation

Isovolumetric contraction begins when the mitral valve closes (at the first heart sound, S1) and ends when LV pressure exceeds aortic diastolic pressure, opening the aortic valve. During this phase, both mitral and aortic valves are closed, the LV contracts isometrically, pressure rises steeply but volume remains constant (no flow in or out). This phase represents the highest rate of LV pressure rise (peak dP/dt) and is energetically costly. Option A has aortic valve open (incorrect); option C suggests simultaneous opening (incorrect); option D describes filling phase.

Reference: Guyton & Hall, Textbook of Medical Physiology, 14th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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